


Dear Hearts and Gentle People: Heat (NSFW)

by Esuerc



Category: Undertale (Video Game)
Genre: Accidental Voyeurism, Blow Jobs, Breast Fucking, Clothed Sex, Collars, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Ecto-Tongue (Undertale), Ectobiology, F/M, Knotting, Masturbation, Mating Cycles/In Heat, Multiple Orgasms, Naked Female Clothed Male, Oral Sex, Skeleton Sex (Undertale), Undertale Skeletons in Heat, Vaginal, Vaginal Sex, Wall Sex, character is female with female parts, human is not frisk
Language: English
Status: Completed
Published: 2019-06-21
Updated: 2019-06-21
Packaged: 2020-05-15 23:13:59
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,353
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19305814
Author URL: https://archiveofourown.org/users/Esuerc/pseuds/Esuerc
Summary: Mutt was in heat.Normally, he could deal just fine. He'd get himself off, find someone willing, or just power through it. But now that there was a human living in the house, he was finding it hard to control himself.Too bad said human finds out by accident.





	Dear Hearts and Gentle People: Heat (NSFW)

**Author's Note:**

> I have more NSFW chapters for Dear Hearts and Gentle People right here:
> 
> https://archiveofourown.org/collections/DearHeartsandGentlePeople
> 
> \--

\--

Kitten/Mutt

\--

 

Your bed always smelled so good.

Mutt pressed his face against your pillow and took a deep breath, his bones hot under his coat just from the smell alone.

It was that time again: it only happened a few times a year, but when it did, Mutt found it hard to control himself, especially now that there was a human living amongst them.

His heat flowed hard through his body, his magic set into overdrive as he did everything he could to get release. He'd gotten himself off multiple times, tried his best not to do anything at all, watched videos, movies--anything he could get his hands on.

But with you there, living with a bunch of monster that could fuck you up in more ways than one?

He found himself drooling on your pillow.

Pressed against your sheets, he'd managed to unbuckle his pants, his sweater and long coat only making him hotter. But he didn't care.

His collar jingled against his chin as his cock was free, his hand slowly moving down its length as he breathed in your scent. He'd always loved that smell, but never tried to take you--Red was too close by most times, hovering around you like some kind of vulture. And Black would tug him away if he got too handsy when others were present.

Right now, though, you were out with Blue, having an evening on the town.

That left your room empty. And even though Mutt was sure Blue would try something of his own, all he needed was your smell and his hand.

He'd get his heat down one way or another.

Thrusting into his phalanges, Mutt bit into your pillow, his sockets screwed shut as he tried to imagine you under him, fucking you hard into the bed.

He cracked one eye open for just a second and sucked in a deep breath. Mutt all but threw himself down onto his back, pulling one of your pillows over his face as he spread his legs.

His cock ached for something tighter, hotter, anything to get this heat down. He just needed to cum in something, on something, it didn't matter.

The heat in his bones was almost unbearable.

Arching his back, he felt himself getting closer, and quickened his pace. He imagined you riding him, taking him as far you could, holding that cunt of yours right on his dick.

His tongue slipped from his mouth. He was practically drooling.

Mutt wanted to look down between you and see you speared on his cock, your pussy full as he thrust up into you.

He thought of you taking his knot, tied to him as he filled you up until you nearly burst, your belly full of his magic even as he felt another bout of his heating rolling in.

Mutt bucked into his hand, envisioning you pulling off him, his cum flowing out of your folds before he plowed back into you for another round.

With a deep groan, he gave a few more thrusts into his hand, and came hard. His magic shot up onto his coat and his hand, his dick still rock hard from his heat.

He bit into your pillow as he rode his high out, his hand still moving across himself. He could go again within a minute or so, the pressure in his pelvis building.

It wasn't until he heard the door to your room creak open that he froze. His marrow ran cold, sockets wide under the pillow he'd been drooling on seconds ago.

Lowering the pillow from his flushed face, his skull lit up as he saw you, standing in the doorway. Your gaze moved from his face down to his still very-erect cock, some feathers from your pillow falling onto his skull.

You simply stated at one another for a few moments, the silence falling heavily on your shoulders. From the bright magic splashed on his coat, you could tell he'd already taken care of matters without you there, though he still looked raring to go.

Before Mutt rolled quickly from the bed onto the floor, he threw the pillow from his face. Shutting the door behind you so no one could see inside, you simply watched as the monster panted hard against the side of your bed. He'd landed hard, but he couldn't tear his gaze from the floor at your feet.

It was then that Mutt gave a nervous chuckle, yanking on the leash of his collar as he let his legs fall to the floor, laid open, "caught me at a moment of weakness, darlin'." His panting was heavy, his skull dotted with beads of sweat and a few feathers.

Still, you stood at the door, pressed against it as though you wanted nothing more than to be alone. **In your room**. Without a monster fucking your pillow until it ripped.

Mutt swallowed hard, his cock straining as he could smell you from where he was at. There was a hint of arousal on you, probably from seeing him getting off on your bed. But there was trepidation in your eyes, something that said you hadn't quite come to a decision on what to do yet.

"it's a heat." Mutt clarified bluntly, staring down at himself, "the others r'gonna have theirs soon, too. can't help it. ain't an excuse, but it is how it is." He ran his tongue along the back of his teeth, "ain't gonna lie. it's not just me who likes the smell of ya. it's Red, too."

Making sure the door to your room was locked, you took a few steps toward Mutt, his hand still tight around his leash. "the heats get hard. nothin' to do but get yourself off or fuck until it's gone. drives some monsters fuckin' crazy." His eyelights trailed from your face, to your chest, down to the apex of your legs, "ain't helpin' that you're here."

At that, you crossed your arms, eyes narrowed down at him. Mutt knew that wasn't the best thing to say, but he was going to be honest.

With you there, the heat was that much worse.

"like I said, I like the smell of ya." He cringed at his own words, and felt his dick shift at the thought of you, of what he'd been imagining before. "s'why I was in here. thought you'd be gone longer."

Speaking of which, Blue's scent was nowhere on you save a faint hint--you two hadn't done anything while you were out.

A thought that made Mutt strangely happy.

Mutt peered up at you through the fur of his hood, extending the handle of his leash out invitingly, "how 'bout this? you take my leash, you an' I'll have a night of it. you say 'nah', I'll get out. your choice."

Fuck, he hoped you'd take the leash.

Silently, you stood there, staring down at the leash in Mutt's outstretched hand. His phalanges curled around it, digging into the leather of the grip. His eyelights darted this way and that, the glow of his cock illuminating the bottom of his face.

Already, the heat in his bones was becoming unbearable. He needed you to make your mind up soon. He wanted release again, but he wasn't going to jump your bones without your say-so. He was a monster, but he wasn't a _monster_.

When your hand reached out slowly, Mutt felt his shoulders fall in relief.

You'd taken the leash.

Moving himself forward, he shimmied on his knees to sit in front of you, his skull angled up to watch your expression. His fingers curled into the fabric of your shirt, long legs spread out to either side of yours as he waited for you to continue.

"darlin', you don't know how much this means," he stopped short, your hand roving under his hood to pet the crown of his skull. That alone was enough to silence him, your touch sending a shiver down his spine.

Leaning into it, you tried to hold back a laugh when his long tongue lolled out, Mutt panting deeply.

He was being serious. The heat was making him burn up even at the slightest of touches.

You stood there for about a minute simply petting him, his sockets shut in bliss as your fingers skimmed along his skull. His breath was hot on your hand, his sharp teeth parted as he continued to pant.

Your touch moved to his neck, scratching at his vertebrae from front to back, his head leaned back as he simply watched your relaxed face.

Mutt wanted you to touch him like that all over. Down his spine, in his rib cage, across his hips. He didn't care where. He didn't want you to stop.

With one gentle yank on his collar, his eyes shot open.

He was fine with stopping.

Clawing his way up from the floor, he towered above you, his cock nearly poking at your belly. He played with his leash, unsure of what to do next.

Mutt decided for you, however, spinning you around. Still holding tight to his leash, he pushed you against the wall, grinding against the fabric of your pants.

His cock found its way between your legs for a moment, his large hands groping up your hips until he moved up and took a breast in each. Even though you were still clothed, it didn't stop him from sliding himself between your thighs.

Mutt's breath was hot above you, fingers fondling wherever he could. Your tits, hips, your waist. And your smell. This close, your scent was intoxicating.

But he needed more.

Removing his hands from your tits, he took hold of the hem of your pants and tugged. They fell down around your ankles, your panties already wet from his previous motions.

Sliding those down at well, he returned his cock back between your thighs and pressed along your lips, your wetness coating him as he pushed forward. You shivered at the sudden intruder betwixt your legs, your breath hitched in your throat.

Soon, he pushed you up against the wall, his collar tight as you tugged his head down, and began to thrust wildly through your clenched legs.

You glanced down as he panted against your neck, watching as the head of his cock appeared and vanished, its girth parting your folds as he moved over your clit.

One of Mutt's hands returned to grab at your breast, the other tight on the curve of your hip. Your breath caught when it moved down to your thigh, hoisting it up over his arm as his other hand moved to hold your hips in place.

Your pants and panties fell to the floor in a heap, your core exposed.

Arms against the wall, he pushed against you rougher, your legs parted in such a way that you felt every ridge of his cock slide against your opening. Mutt was long, his dick as thick as your arm, and dotted with several piercings on its underside. He was larger than any of the other monsters in the house, something that intimidated you somewhat.

He was bigger than Red or Edge, though you still didn't have much to go on concerning monster tackle.

But you trusted him not to hurt you too badly, even given his heat. One shout to Red would end everything, if need be.

For now, though, you enjoyed the feeling of him sliding over your pussy, the piercings on his cock glinting from your wetness.

They were something you'd yet to understand--Red had them, too, and he'd only laughed when you asked.

Magic, he said. It was always magic. Magic enough that you found it hard to walk the day after.

Mutt breathed heavily into your ear, his pace quickening against your core until you felt his hand tighten on your thigh. Breath quick at your throat, you heard him groan deeply as he held your leg just slightly higher.

You weren't going to be the one cleaning up the cum that now dribbled down your wall.

But that hardly stopped him. There was almost no cool down after he came, and within seconds he was back at it again. This time, however, he pulled back a bit longer, the head of his cock angled against your cunt.

He pushed into you, eliciting a quiet moan from your throat as your felt the head push past. One of his piercings made it in, the cold metal rubbing on your walls as he pulled out just enough.

Mutt moved forward again, another inch of him making it inside. You pulled tight on his leash, his tongue lapping against your jaw as he only continued to thrust into you.

"fuck, darlin'." He whined, his cock making it further into your heat, "just a little more. please." The pressure was becoming intense, half of him already inside your aching pussy before he pulled out completely.

You yelped when shoved back into you roughly, your cunt full as your legs quivered. Mutt breathed deep, drooling at the scent of your sex, and began to fuck you in earnest.

Breasts pushed against the wall, he held tight to your hip, your leg angled in such a way that he pushed as far as he could inside. Your face was flushed, the cool of the wall a blessing on your cheek as he took control.

The last thing you needed was Red or Blue trying to text you, or stars-forbid, come into your room. A locked door would stop that smaller skeleton, but Red? That boy didn't know the meaning of privacy.

You screwed your eyes shut, your walls tightening as you felt an orgasm coming. Mutt was still going strong, the bundle of nerves just inside you raw as the ridges of his cock rubbed roughly on it.

You yanked the leash as you came hard, Mutt savoring the way you quaked around him.

He continued to fuck you through your high, your walls spasming around him with each thrust. He could feel you squirm, your leg trembling in his hold.

He came right after you, his magic spilling into your cunt as he continued to move. With each push, his magic slid out onto the floor, bright and hot as there was no sign of stopping. It was blazing inside you, the bright orange cum slowly sliding down your thigh as he hadn't stopped pounding.

He let your leg relax and set it back down. From there, he took your hips with both hands and kept going, watching himself disappear inside you.

You were so tight around him, his heat blurring the line between pleasure and straight-up wanting to pass out. Instead, he slammed into you harder until he felt himself tighten again.

Releasing another load, he pulled out just as the last bits of cum left him, landing on the slope of your ass. He was mesmerized by the sight, the glow of his magic on your ass and flowing from your flushed pussy.

You breathed heavily, your heart racing in your chest. Deep down, you knew this was only the beginning of what Mutt wanted, needed. If his heat was bothering him so bad that he'd already released several times, once before you'd even gotten there, then obviously he needed a little assistance.

Pushing from the wall, you stepped out of your pants and turned toward him, pushing him back toward the bed by the chest. Honestly, he seemed surprised, his hand wrapped around his leash as you held it firmly.

He fell back onto the bed, sitting up on his elbows as he watched you kneel in front of him.

His teeth parted as you began to stroke him, your hand barely able to wrap around his girth. He let himself fall completely as you ran your tongue up his length, taking the head of it into your mouth.

Mutt clawed at your comforter, his sockets shut tightly as one of your hands snaked up his shirt to rub at his spine. His head fell to the side as he brought up a hand to stroke at the top of your head.

You hummed around his cock as you stroked what wouldn't fit in your mouth, your head pressed down slightly as Mutt tried to push further in. But you wouldn't let him, grazing your teeth across his dick when he got too assertive.

He backed down immediately, a nearly silent whimper leaving him as his hips moved on the bed. He was getting close, and with a few more scratches along his spine, he came. Shooting onto your tongue and down into your throat, you let his cock pop out of your mouth before he finished. The rest landed on your neck and chin, you throat tight as you attempted to swallow the remainder.

Already, he'd come over and over, and still Mutt was standing at attention. You pulled yourself up from the floor and slid onto the bed, sure to run your pussy along him as his hands came up to grab you.

He moved you forward until his cock sat just between your legs, his sharp teeth parted as he panted heavily. He still had plenty of magic left in him waiting to burn off, and you were more than accommodating.

Yanking you forward by the shirt, his teeth pressed against your lips, his tongue sliding out to push into your mouth. You barely had time to breathe as he tasted himself on you, his ecto tongue nearly at your throat.

Quickly, he rolled the two of you over and pushed himself inside you again, pulling back from your mouth to run his tongue along the line of your neck.

Almost violently, he fucked you, his cock sliding easily into your abused cunt as his teeth raked at your skin. Grabbing hold of his collar directly, you held him close to you, his whole body hot against yours.

"fuck, fuck, fuck, darlin, pull harder'." He groaned at your neck, face pressed into your bed as he thrust as deep as he could. You tugged his collar roughly, making him whine before he unloaded again inside you.

This time, he held himself in place, sitting up as he continued to slide into you. One of his hands roved down between your legs, finding that sensitive nub, and rubbing at it until you tightened around him.

Your orgasm milked him as he sat still. Already, he could feel some of his heat wearing down, his continual releases taking effect. And there you were, willingly helping, letting him take it all out on you without fully understanding it all.

Mutt knew why Red loved you so much.

Gently, he moved inside you, feeling your walls relax somewhat after your orgasm. He still couldn't stop, he still needed release. But he was getting there.

Allowing his hands to rove up your shirt, Mutt pulled it off you, leaving you in just your bra. One of his hands snaked across them, feeling your pert nipples just under the fabric.

Pulling on his collar again, he pulled out of your cunt and moved forward, his cock bobbing between your tits. Without hesitation, he moved the band of your bra up a bit, just until your breasts barely sat inside, and ran his length between them.

Your hands came up to rub across his thighs, his own pressed down on either side of your head as his hips thrust forward.

The head of his cock pushed at your chin, your hands now pushing your tits together until you covered him. He stared down at you hard, taking the initiative to fuck your tits with a little more vigor.

Mutt leaned forward, allowing himself to slide quicker between your breasts, your skin coated with a light sheen of cum and sweat, from both you and him. Opening your mouth, you ran your tongue along what you could, his dick coming up to meet you.

His face scrunched, fingers digging into your sheets as he quickened his pace. Deep down, he wanted to know what it would feel like if he and his brother took you. Or what about the others' heats? Would eight monsters trying to fuck you at the same time be too many?

That was too many, right?

A few more seconds, and he came again, spilling across your tits and neck even as you moved your hands to continue pumping him.

Mutt felt a familiar tightness in his pelvis, knew that he was close to finishing what he had. He just needed one or two more releases.

Sliding out from your tits, he took your legs and pushed them forward, up toward your shoulders. He bent you as far as you could comfortably go, his thighs keeping your legs in place as he angled his cock toward your pussy again. Thrusting down, he pushed deep, your walls clenching at the new position.

One of his hands moved up to your belly, glowing brightly in the room as an unfamiliar magic pulsed into your body. You felt Mutt push even deeper than before, sliding the rest of his cock inside you before you even knew what was happening.

You tightened around him at the sensation, the feeling of his entire length in your cunt, unsure as to how he'd done it. There was no physical way you'd taken the whole thing, from head to base, and yet his hips slapped against your ass with ease.

You knew he'd say magic if you asked.

He handed you his leash again, his phalanges slightly shaking before he moved inside you. Pulling on his collar, you moaned at the feeling of every piercing on his length moving inside you.

Keeping your legs down with his hands, he fucked you into the bed, his tongue dangling from his mouth as he watched your tits bounce. He bottomed out inside you every time, a heat building in his pelvis.

Maybe they could take turns? Two or three at a time? Surely, you could handle that? Really, Mutt just wanted to be in on it, either if he was doing it himself or just watching. Seeing Black pushing into you would be a sight, he knew.

He was getting close. With a few more hard thrusts, he came again, your pussy clenching at his release, the excess magic flowing down from your pussy across your ass.

Mutt pulled the entirety of his cock out and let it bounce in front of you. Looking at it then, you still didn't know how you took it all. All you _did_ know was that you felt empty without it inside you.

Just one more. One more time, Mutt told himself. He wanted to knot, to spill into you until he had nothing left, and then, hopefully, he could make due with his heat.

The other skeletons would have to manage their own way.

Mutt bent low so his face was next to yours, his hips moving even as he whispered at your neck. He slid back into you, all the way down to the base again, and groaned deeply at the feeling. You joined him, your fingers digging into his ribs, his spine, anywhere you could grab.

Your hands moved down and held at the bed sheets, your face hot and chest heaving. Already, you could feel a swell building at the base of Mutt's cock, and you knew from Red what would come next.

Mutt moved quickly, taking your pussy harder than ever. He clutched at your hips, ramming deep inside you as his tongue dangled from his mouth and across your neck.

"fuck, darlin'. gonna… gonna fuckin'," it was getting hard for him to form a coherent sentence, the base of his cock beginning to widen, "just a little more. gonna fill you up, fucking knot."

Mutt wasn't sure if you understood what he meant. He didn't know if Red had done the same with you before. If he knew the other skeleton right, it wouldn't have been the first time.

Regardless, his pushed as deep as he could, his knot forming bit by bit until his thrusting became sporadic.

You felt him begin to build, your hand moving down between your legs to rub at your clit. Combined with his cock, you were sent over the edge. He watched your tits bounce with each thrust, your face dyed with a deep blush.

Mutt sucked in a breath as your cunt tightened around him, his thrusts wild as his hips slammed into your ass.

Soon, he felt his knot nearly formed, and one last push, he shoved into you, his knot pressing past your tightness as he came hard.

His cum spilled into you like before, though this time, his knot kept any from escaping. Mutt kept your legs pinned open, the weight of his frame pressed against you as he continued to unload inside your pussy.

Your arms came up to circle around his neck, pulling him close as he relaxed on top of you. He nuzzled against your neck, enjoying the way your hand rubbed at the back of his skull.

Mutt sighed, letting his magic flow into you as the heat in his bones began to die down. He knew it was only temporary, but a great deal of the edge had been taken off.

Knotted, he knew he wasn't going to be moving any time soon, but you didn't seem to mind. All he did know was that he enjoyed your gentle pets against his skull, down the back of his neck.

At least he knew he had someone to go to from now on, if you were still willing.

And with the other monsters going into heat soon, he'd admit he was excited to see what kind of mischief you'd get thrown into, especially with Red or Blue.

Mutt smirked against your neck, his brow pressed against your cheek.

He hoped you liked being stuck that way for a little while.

Because he was going to sleep.


End file.
